s place instantly. Here is again,
evidence of either an absorption of some material agent from the
sunbeam, or an alteration in the chemical constitution of the body. It
was from understanding these principles and applying them that
philosophers were enabled to produce the Calotype, Daguerreotype, &c.
For the effects and action of light on the camera, see Chapter V.

Some advances have been made towards producing Photographic impressions
in color--the impossibility of which some of our best and oldest
artists have most pertinaciously maintained. The colored image of the
spectrum has been most faithfully copied, ray for ray, on paper spread
with the juice of the Cochorus Japonica, (a species of plant) and the
fluoride of silver; and on silver plate covered with a thin film of
chloride. The day may be still remote when this much to be desired
desideratum shall be accomplished in portrait taking; but I am led to
hope that future experiments may master the secret which now causes it
to be looked upon, by many, as an impossibility.

That great advantages have resulted, and that greater still will result
from the discovery of the Photographic art, few will deny. The
faithful manner in which it copies nature, even to the most minute
details, renders it of much value to the painter; but a few minutes
sufficing to take a view that formerly would have occupied several
days. Its superiority in portraits, over miniature or oil painting has
been tacitly acknowledged by the thousands who employ it to secure
their own, or a friends likeness, and by the steady increase in the
number of artists who are weekly, aye daily springing up in every town
and village in the land.

CHAP. III.

SYNOPSIS OF MR. HUNT'S TREATISE ON "THE INFLUENCE OF THE SOLAR RAYS ON
COMPOUND BODIES, WITH ESPECIAL REFERENCE TO THEIR PHOTOGRAPHIC
APPLICATION."

OXIDE OF SILVER exposed for a few hours to good sunshine, passes into a
more decided olive color, than characterises it when first prepared by
precipitation from nitrate of silver. Longer exposure renders this
color very much lighter, and the covered parts, are found much darker,
than those on which the light has acted directly. In some instances
where the oxide of silver has been spread on the paper a decided
whitening process in some parts, after a few days exposure, is noticed.
Oxide of silver dissolved in ammonia is a valuable photographic fluid;
one application of a strong solution form